1. Field of Invention
The invention relates to an apparatus and method for cutting vegetation. More specifically, the invention relates to an apparatus and method for cutting vegetation with focused laser beams.
2. Description of the Related Art
Prior mowing devices include gasoline powered motors driving rigid, moving cutting blades operated by a series of drive spindles, belts, drive shafts, and gearing devices. Prior rotating cutting blades require periodic sharpening of the blades and periodic replacement due to impact with rocks and the ground. The power producing motors and cutting blades require speed limitations imposed by industry safety standards on the engine and/or blade rotation mechanisms to limit blade tip speeds as a function of the length of the mower blade as a safety measure for limiting the damages to adjacent objects or the operator when blades impact and shatter against hard objects. Therefore, if the speed of travel of the mowing device increases past a certain ground speed along the surface being mowed, the rotating blades will not increase proportionally in rotational speed so the effective cutting of all standing grass may diminish at high ground speeds. Commercial mowing operations would benefit from a cutting apparatus that incorporates a cutting means that increases in rotational speed as the ground speed increases, with no limitation to the rotational speed of the cutting means.
The gasoline powered motors and rotating cutting blades are noisy when operated, and are relatively heavy and cumbersome to operate due to the weight of the motors, drive spindles, belts, chains, and rotating cutting blades. If adjustable heights of blades are needed to provide for a mulching effect, the rotating cutting blades must be maneuvered manually to a different cutting height, or multiple passes are required over the vegetation to produce smaller sized clippings for effective mulching of the vegetation.
An example of the prior art is U.S. Pat. No. 4,952,222, issued to Tobias, which discloses a grass cutting device with an electrically activated energy path such as strands of wires between spaced electrodes that intersect blades of grass and sears off the grass tips at the contact points. The strands of wires or electrodes are supported by a support means adapted to rest on or in close proximity to the ground. The device also discloses a method of grass cutting including establishing a grass cutting energy path at a location proximate the ground for severing the upper portions of grass blades. The grass cutting energy path can alternatively include a laser having a laser beam path directed by generally stationary mirrors to extend the laser beam path horizontally within the mower housing between mirrors at a location parallel to the ground. The laser beam may be diminished in intensity and misdirected by reflections off of vibrating mirrors within the mower housing, and may be deflected by the multitude of wet or dry grass blades within the laser beam path as the beam is directed parallel to the ground between mirrors and reflectors.
Another example of the prior art is U.S. Pat. No. 4,338,744, issued to Gilmore, which discloses a weed destroying system having electrodes for contacting weeds adjacent rows of crops along which the vehicle travels. The vehicle includes a high voltage generator for supplying high voltage to the electrodes. The weed destroying system includes a safety system to minimize the possibility of electrical shock hazards to the operators.
Another example of the prior art is U.S. Pat. No. 3,652,844, issued to Scott, Jr., which discloses a method and apparatus for destroying weeds and other plants by application of a pulsed laser beam directed onto vegetation by a diverging mirror arrangement. The laser beam is directed horizontally or vertically onto aquatic vegetation to be destroyed by a pulsed laser unit such as a N.sub.2 --CO.sub.2 --He laser focused onto an arrangement of mirrors adjusted by a mechanical means for focusing the laser beam. The weed destroying system produces cellular damage by build-up of heat within the aquatic vegetation on which the pulsed laser beam is focused.
A need exists in the vegetation control industry for a reliable, portable cutting apparatus that cuts vegetation at different heights during passage over the vegetation, that does not generate excess noise, and that includes a minimum of moving parts.
Therefore, it is an object of the present invention to provide a cutting means for cutting vegetation at different heights during rotation of the cutting means.
It is another object of the present invention to provide an apparatus having a cutting means rotatable at increasing speeds in proportion to the speed of the apparatus along the surface covered by vegetation.
It is another object of the present invention to provide an apparatus having a cutting means that includes a minimum of belts and rotating blades.
It is another object of the present invention to provide an apparatus having a cutting means that does not generate excess noise and minimizes use of moving blades.
It is another object of the present invention to provide a method for operating a cutting means for cutting vegetation at different heights during each passage of the cutting means.
It is another object of the present invention to provide a method for operating a cutting means for cutting vegetation into small clippings of different lengths for improved mulching of the cut vegetation.